1. Field of the Invention
The present invention relates to a control system and method of a hybrid vehicle which is driven by an engine and an electric motor, and in particular, to a system and a method for preventing a decrease of the remaining battery charge while driving in a traffic jam.
2. Description of the Related Art
Conventionally, a hybrid vehicle having not only an engine but also an electric motor as the drive source is known.
As a hybrid vehicle, a parallel hybrid vehicle is known that uses an electric motor as an auxiliary drive source for assisting the engine output. In the parallel hybrid vehicle, typically, operation of the engine is assisted using the electric motor during the accelerating operation, while during the decelerating operation, the battery and the like are charged via a regenerating operation, that is, xe2x80x9cdeceleration regenerationxe2x80x9d is performed. According to various control operations including the above, the remaining battery charge (called a xe2x80x9cSOC (state of charge)xe2x80x9d, hereinafter) of the battery is maintained while also satisfying the driver""s demands. An example thereof is disclosed in Japanese Unexamined Patent Application, First Publication, No. Hei 7-123509.
When such a conventional parallel hybrid vehicle drives at a medium or high speed, sufficient regeneration energy can be obtained during deceleration. However, if the vehicle repeatedly starts and stops at a low vehicle speed, problems relating to the power management may occur.
That is, when the vehicle repeatedly starts and stops, decelerating operation starts before the vehicle speed becomes sufficiently high; thus, sufficient regeneration energy cannot be stored. During a traffic jam or the like in which each vehicle has to repeatedly start and stop at a low vehicle speed, sufficient charge (obtained by deceleration regeneration) cannot be obtained.
In consideration of the above circumstances, an objective of the present invention is to provide a control system and method applied to a hybrid vehicle, by which an excessive decrease of the remaining battery charge can be prevented while driving in a traffic jam.
Therefore, the present invention provides a control system of a hybrid vehicle, wherein:
said hybrid vehicle comprises:
an engine (for example, an engine E in the following embodiment) and a motor (for example, an motor M in the following embodiment) for outputting force for driving the vehicle;
a battery device (for example, a battery 3 in the following embodiment); and
a charging device (for example, the motor M in the following embodiment) for charging the battery device, and
said control system comprising:
a remaining battery charge detecting section (for example, a battery ECU 31 in the following embodiment) for detecting the remaining battery charge (for example, remaining battery charge QBAT in the following embodiment) of the battery device;
a traffic-jam drive determining section for determining whether the vehicle is driving in a traffic jam (refer to step S105 in the following embodiment); and
a control section for making the charging device charge the battery device if the remaining battery charge of the battery device, detected by the remaining battery charge detecting section, is below a first predetermined value (for example, un upper limit #QBJAM in the following embodiment), and if it is determined by the traffic-jam drive determining section that the vehicle is driving in a traffic jam.
The present invention also provides a control method of a hybrid vehicle having the above structure, comprising the steps of:
detecting the remaining battery charge of the battery device;
determining whether the vehicle is driving in a traffic jam; and making the charging device charge the battery device if the detected remaining battery charge of the battery device is below a first predetermined value, and if it is determined that the vehicle is driving in a traffic jam.
Accordingly, while the battery device is charged, no power is supplied to the motor, so that it is possible to prevent an excessive decrease of the remaining battery charge of the battery device.
In a typical example, the traffic-jam drive determining section comprises:
a maximum speed detecting section (for example, an FIECU 11 in the following embodiment) for detecting a maximum vehicle speed during a single driving operation (or movement) from the vehicle start to stop (for example, a maximum vehicle speed DRVMAX in the following embodiment); and
a throttle opening-degree detecting section (for example, a throttle opening-degree sensor S6 in the following embodiment) for detecting a degree of throttle opening (for example, the degree of throttle opening TH in the following embodiment) of the engine, and
the traffic-jam drive determining section determines that the vehicle is driving in a traffic jam if the maximum vehicle speed during a single driving operation is equal to or below a predetermined value (for example, an upper limit vehicle speed #VJAMST in the following embodiment), and if the degree of throttle opening is equal to or below a predetermined value (for example, an upper limit degree #THJAM in the following embodiment).
Similarly, the step, of determining whether the vehicle is driving in a traffic jam may comprise the steps of:
detecting a maximum vehicle speed during a single driving operation from the vehicle start to stop;
detecting a degree of throttle opening of the engine; and
determining that the vehicle is driving in a traffic jam if the maximum vehicle speed during a single driving operation is equal to or below a predetermined value, and if the degree of throttle opening is equal to or below a predetermined value.
Accordingly, if it is determined that the vehicle is driving in a traffic jam as described above, and if the remaining battery charge of the battery device is below the first predetermined value, the battery device is charged and thus it is possible to prevent an excessive decrease of the battery device.
In another typical example, the traffic-jam drive determining section comprises:
a maximum speed detecting section for detecting a maximum vehicle speed during a single driving operation from the vehicle start to stop, and
the traffic-jam drive determining section determines that the vehicle is driving in a traffic jam if the maximum vehicle speed during a single driving operation is equal to or below a predetermined value, and if the remaining battery charge of the battery device, detected by the remaining battery charge detecting section, is equal to or below a second predetermined value (for example, remaining battery charge #QBJAMST in the following embodiment) which is smaller than the first predetermined value.
Similarly, the step of determining whether the vehicle is driving in a traffic jam may comprises the steps of:
detecting a maximum vehicle speed during a single driving operation from the vehicle start to stop; and
determining that the vehicle is driving in a traffic jam if the maximum vehicle speed during a single driving operation is equal to or below a predetermined value, and if the detected remaining battery charge of the battery device is equal to or below a second predetermined value which is smaller than the first predetermined value.
According to the above conditions, it can be determined that the remaining battery charge of the battery device has been excessively consumed regardless of the degree of throttle opening, and the battery device can be immediately charged, thereby much more reliably preventing an excessive decrease of the remaining battery charge.
After it is determined that the vehicle is driving in a traffic jam according to any method as explained above, the traffic-jam drive determination may be released if the vehicle speed becomes equal to or above a predetermined value, or if the vehicle speed is below a predetermined value and the degree of throttle opening becomes equal to or above a predetermined value. Accordingly, the traffic-jam drive determination can be quickly released immediately after it is determined that the vehicle has been escaped from the traffic jam.
In the above structure, preferably, the motor also functions as the charging device, and the battery device stores energy generated using the motor as a generator driven by the engine, and energy regenerated via a regenerating operation performed by the motor when the vehicle is decelerating. In this case, the operation of charging the battery device can be reliably performed because the motor which functions as the charging device stops the original motor operation. In addition, the space in the engine room can be effectively used.
In addition, the control section may prohibit or restrict the operation of outputting force by the motor if the remaining battery charge is below the first predetermined value, and if it is determined that the vehicle is driving in a traffic jam.
Similarly, in the control method, the operation of outputting force by the motor may be prohibited or restricted if the remaining battery charge is below the first predetermined value, and if it is determined that the vehicle is driving in a traffic jam.
Furthermore, the control section may set the amount of the charge performed by the charging device to a high charge level if the remaining battery charge is below the first predetermined value, and if it is determined that the vehicle is driving in a traffic jam.
Similarly, in the control method, the amount of the charge performed by the charging device may be set to a high charge level if the remaining battery charge is below the first predetermined value, and if it is determined that the vehicle is driving in a traffic jam.